I have a 15:1 gear box crank winder and I was thinking of making some of them.
The pictures below are of a 5:1 which might be easier to go for 5:1 on the first batch.
I’ve got a bunch of these and I give them to kids as prizes sometimes or donate them to the more needy kids.
I rarely show them to children during my model plane workshops because I want them to learn to hand wind and get their planes flying well first. I think it’s time to make a DIY rubber band winder.
To see how these things are used have a look at the video here on how to make a Squirrel Model Airplane fly very far.
As you can see the elastic is on the propeller hook which is in turn hooked into a “winding stooge”. The elastic is stretch wound with the winder, then just hooked on the model.
The winders are just two shafts, a housing and some gears. The gears don’t have to be enclosed.
I could probably make one out of hardboard by cutting a handle with two holes in it for shafts. Then add some gears and shafts. I suppose some washers so the wood doesn’t rub. Also the hook that goes to the plane will be under a bit of tension. I suspect a couple of small washers can take up that thrust. I’m sure there will be lots of configurations of the gears to experiment with (and handle positions relative to the crank). The only thing that looks tricky is that the shaft with the hook has to be attached to the small gear. The other gear can just freewheel. I know there will be an elegant way of attaching the small gear to the elastic.
I want to have a nice hand crank design on hand.
After that I will make an electric design. A motor will do the winding for you. Perhaps an Arduino based one that counts for you or can measure torque. Actually a direct drive dc motor is probably a very simple solution. Perhaps pwm motor controller can give a precise static torque so the motor will wind the same each time. A stepper is good for winding a specific number of turns but I don’t that that’s very efficient. Probably if we’re interested in turns we could have a sensor at the output shaft.